In NYS, unless things have changed, a student-athlete can play on varsity teams as early as 7th grade, though VERY few ever do. In order to be eligible, a person has to pass a physical fitness test (running a mile, broad jump, situps, etc.) and be deemed good enough to compete by the coach of the respective sport. Middle schoolers on high school level teams happens in smaller schools and it RARELY happens in football, but it often happens in wrestling and girls hoops and girls soccer and both girls and boys track.